Radiotelephony



' missile-a Apr. 19, 1921. 15,089.

C. R. ENGLUND.

7' RADIOTELEPHONY.

APPLICATION FILED MAR- 3, 1920- /n venfor: Car/ R. Eng/and.

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UNITED STATES PATENT OFFICE.

CALL 1. ENGLUND, OF EAST ORANGE, NEW JERSEY, ASSIGNOB TO AMERICAN TELEPHONE AND TELEGRAPH COMPANY, A CORPORATION OI NEW YORK.

BADIOTELEPHONY.

Original m. 1,253,543, dated March 5, 191a, Serial reissue med mirth a, 1920. Serial 110. 882,961.

To all whom it may concern: Be it known that I, CARL R. ENGLUND, a citizen of the United States, residing at East Orange, in the county of Essex and State of New Jersey, have invented certain new and useful Improvements in Radiotelephony, of which the following is a full, clear, concise, and exact description.

This invent n relates to radio telephony, and in particu ar to a system of transmission in which only the modulated portion of a high frequency wave is radiated from the antenna. In radio telephony it has been customary to establishin a circuit a high frequency oscillation and to modulate-the .amplitudeof this oscillation in accordance with a signal to be transmitted. Now, it is well-known that when a high frequency carrier wave of frequency 0 is modulated in accordance with a signal wave of frequency S, the resultant wave radiated from the antenna is made up of three parts of frequencies (1-8. G and C-l-S, which components may be considered to be transmitted simultaneously through theether. It has been proposed as described in British specification No. 17,170 of 1916 of which the serial number under the new British system of consecutive numbering, is 102,503, to eliminate from the antenna the unmodulated component of fre-, quency C, and to transmit onl the modu lated portions represented by t 'e other two components. When this method is adopted 85 the radiated wave-is spoken of as a pure 'modulated wave. The great advantage of this method is that the waste of power rep-- resented by currents of frequency 0 in the antenna is eliminated, and that there is some ain in the quality of received oscillation. n order to receive signals sent in this manner it is necess'ar to include at the receiving station, in a dition to the usual, apparatus, a small generator capable of delivering currents of the eliminated frequency 0, but since only a very small amount of power of this f uency is required at the receiving station, t e auxiliary generator at that station need have but an extremely small power output.

. In the specification above referred to, a certain method of eliminating the unmodulated component of the carrier wave is given, and this invention proposes still an- Speciflcatlon of Reissued Letters Patent. Reissued Apr. 19, 1921.

No. 83,504, filed March 11, 1916. Application for lation of carrier frequency which is equal in amplitude but opposite in phase tothe oscillation of carrier frequency which represents the unmodulated portion of the 'wave to betransmitted. By this'means the component to be eliminated from the antenna is neutralized in the apparatus between the primary modulating source and the antenna.

The invention, will be more particularly described in connection with thedrawing, in which Figure 1 represents a transmitting stat on constructed in accordance with this invention and Fig. 2 showsa form of receiving station by which the modulated waves may be received. This receiving station forms no part of this invention. 7

Referring to Fig. 1, 1 is a generator of oscillations of the frequency C and 2 a transformer by means of which these oscillations are impressed upon' the input circuit of a thermionic modulator 3. 4 is a microphone circuit, the variations of current in which are impressed upon the same input circuit through the transformer 5'. The result of this arrangement is, as is now well-known, to produce in the output circuit of the modula-tor' 3 a high frequency current whose amplitude is modulated in accordance with the alternating currents set up in the microphone circuit. This output circuit is connccted'through transformer 6 to the common input circuit of a number of thermionic amplifiers 7 arranged in parallel, their common output circuit bein coupledthrough transformer 8 to the radlating antenna 9.

The system so far described is characterized bythe fact that currents of all three of. the above mentionedfrequ'encies occur in the antenna 9. By means of the apparatus next to be described the component of frequency Cis prevented from reaching the antenna by being neutralized in the in ut circuit of the amplifier 7. To accomp ish this, the input circuit of the amplifier 10 is connected through an autotransformer 11 to the terminals of the generator 1, the purpose .of this autotransformer connection being to regulate the voltage irnpressed upon the input circuit of the amplifier 10. he output circuit of the latter is connected to a phase regulating device 12, which may be of any suitable form, and the voltage appearing across a section of this. network is then applied to the common input circuit of amplifiers 7. It will be clear that this latter voltage will have the frequency C of oscillations produced by the generator 1, and

that theseinay be so regulated as to intensity and phase that they shall exactly neutralize the component of frequency G appearing, in

. of the modulator.

the input circuit of amplifiers 7 and prevents its appearance in the output circuit Currents of the frequency C will therefore not appear in the antenna 9. In case the amplifier 10 or the qusted that the neutralizing current is ex-' base regulating device l2'are not so adergy would be radiated in the form of waves of frequency C. The expressions equal in intensity and opposite in phase should, therefore, be taken to mean. substantially equal in intensity and substantially opposite in phase. 7 a

Referring'to Fig. 2, 14 is a receiving antenna coupled to a resonant circuit 15 tuned to the frequency C of the waves to be received. 16 is a thermionic detector whose output circuit is connected through a transformer to the translating device 17. It will be clear that thewavesareceived by this system will lack thecomponent of frequency C, and the function of the auxiliary generator 18 is to supply small oscillations of this frequency. The circuit of this generator may coupled in any suitable manner to the'antenna14 or to the resonant circuit 15. ,',';Although this invention has been described as applying to radio telephony it .will be clear to those skilled in the art that a wire telephone line may be substituted for the antenna 9 without departin from I, the spirit of this invention. It will urther I opposite phase,

be obvious that manyother circuit arrangements may be devised by means of which the oscillation of frequency 0 may be neutralcircuit of the amplifier 7. What is clalmed is:

1. A radio transmitting system comprising in combination means for generating and modulating high frequency oscillations, means forimpressmg u 11 said modulated oscillations an unmodu ated oscillation of and means for ampligving and transmitting the resultant of sai oscillations.

2. A radio transmitting system comprising in combinationv and modulating high frequency oscillations, means for neutralizing the unmodulated component ofsaid modulated wave, and

means for amplifyin opposing the varied waves and transmitting the resultant lated componentgof said in superimposing thereon an unmodulated means fOl generating and transmitting the modulated portion of said wave.

The method of transmission which comprises variably amplifying a wave and opposing said amplified wave by another wave of constant amplitude.

4. The method of transmitting energy, which comprises producing a wave, modi ing said wave in accordance with speech, producing a second wave of constant amplitude, and causing said modified wave and said constant amplitude wave to oppose each other'in a transmission circuit.

5. The method of transmitting energy,

a which comprises producing a wave, variably .ampllfying said wave,

producing a second wave, amplifying said second wave by a constant amount, and causing said amplified waves to oppose each other.

6; The method of telephony which comprises subjecting periodic energy to speech variations and opposin the resulting varied energy by unvaried energy of similar character. r

7 The method of transmission which comprises varying waves non-periodically,

resulting varied waves by unwaves.

8. Themethod of transmitting energy which comprises modulating a carrier wave in accordance with speech to produce a modulated. carrier wave and opposing said Q modulatedwave by an unmodulated wave to neutralize the unmodulated portion of said modulated wave. d

9. The method of signaling which comprises causing a. high frequency wave to traverse an impedance, varying themagnitude of said impedance in accordance with speech,

causing a second wave of the same frequency to traverse an impedance of substantially constant magnitude and causing said waves to'thereafter oppose each other. 10. The method of transmission comprising producing an unmodulated wave, modulating said wave in accordance. with a nonperiodic current to wave, and neutralizin the unmodulated component of said ,mo ulated wave by impressing thereon an unmodulated wave of an amplitude equal to that of said component', and of the frequency of said first unmodulated wave.

11. The method of sists in generatin tinuous wave mo ulating said wave in accordance with speech to a lated wave," and neutralizgiig the unmodus ulated wave by wave of an amplitude equal to that of said component and of the frequency of said continuous wave. 1

12. A transmission system comprising produce a modulated signaling which cona high frequency cont roduce a modu means for producing and variably amplifying a wave, and means for opposing 881d amplified wave by another wave of constant amplitude.

13. An ener transmission-system comrising means r producing a wave, means or modifying said wave in accordance with speech, means for producing a second wave 1 of constant amplitude, and means for causing said modified and said amplified waves to oppose each other.

14. An ener transmission system comprising means gr producing a wave, means or variably amplifying said wave, means for producin asecond wave, means for amplifying sai second wave by a constant amount, and means for causing said amplified waves to oppose each other.

15. A telephone system comprising means for producing periodic energy, means for varyin said energy in accordance with speech, an means for opposin ing varied ener by unvaried similar characteristics.

16. A transmission system comprising means for producing a wave, means for varyin said wave non-periodically, means for pro ucing an unvaried wave, means for opposing the varied wave by said unvaried energy of wave and means, for transmitting the resultant wave.

17. Means for transmitting energy comprising a carrier wave source, means for modulating waves produced by said source inaccordance with speech, and means for opposing said modulated waves by unmoduthe resultlatedwaves to neutralize the unmodulated portion of said modulated waves.

.a modulated wave, and means for neutralizing the unmodulated component of said modulated wave by impressing thereon an unmodulated wave of an amplitude equal to that ofsaid component and of the frequency of said first-named unmodulated wave.

20. A signalin system comprising means for generating afiiigh frequency continuous wave, means for modulating said wave in accordance with speech to produce a modulated.wave, and means for-neutralizing the unmodulated component of said" modulated wave by superimposing thereon an'unmodulated wave of an amplitude equal to that of said component and of the frequency of said continuous wave.

In witness whereof, I hereunto subscribe my name this 26th day of February, 1920.

CARL R. ENGLUND. 

